This spool rack was designed to be mounted inside of a cabinet using two sections of Schedule 40 3/4" PVC pipe, metal conduit, or even 3/4" wood dowels for longer shelves. In the photo shown the shelf is nearly 34" long and the PVC pipe is starting to sag, so I will be replacing it with wooden dowels for a nice look and added strength.
The design uses two pieces of pipe for each shelf so filament spools of all sizes can fit on top for easy access.
It is mounted inside the cabinet using #6 countersunk flat-head wood screws. First mount the shelving brackets using the center screw for alignment, then level the bracket and install the other two screws for stability and strength.
This is a very simple print, no special settings needed. You require two parts for each shelf.